Questions about the construction and analysis of protocols and algorithms for secure computation and communication (including authentication, integrity, and privacy aspects).
Cryptography studies techniques for secure computation and communication, i.e. secure storage and manipulation of information, both theoretical and practical.
The purposes of cryptography include confidentiality (leading to encryption), data integrity (leading to hash functions), authentication and more. Cryptography often relies on algorithms based on mathematical operations to transform data. Cryptography also includes the study of secure communication protocols.